This disclosure relates to oriented graphite films, methods of manufacture thereof and articles comprising the same.
Carbon fibers have excellent mechanical, electrical and thermal characteristics, which have made them useful in a wide variety of commercial applications. In recent years, they have been investigated as materials of choice for thermal conduction or for use as electrodes for fuel cells. Carbon fibers generally comprise microfibril aggregates aligned in parallel to the longitudinal direction of the fibers and therefore possess anisotropic electrical and thermal properties. Thus, in order to utilize the carbon fibers and their properties effectively, it is desirable to use them in the appropriate orientation for the particular application.
Oriented carbon fibers are often used in composite films. However, these composite films have contact problems with electrodes or substrates that are opposedly disposed to the end faces of the carbon fiber, particularly used in electrical and/or thermal applications. The problem is that the electrical/thermal resistance caused at the contact point leads to a considerable reduction of the application characteristics as a whole. The high crystallinity and the hardness of carbon fibers that produce excellent thermal and electrical conduction characteristics, make it difficult for the end face to contact the opposing surface, which results in a reduction of the effective electrical/thermal contact area. It is therefore desirable to improve the ability of the end face of the carbon fibers to contact an opposing surface, while at the same time preserving the crystalline content and the hardness of the carbon fibers.